Microsoft Corp. will buy wind power from a new Illinois wind farm for the next 20 years to offset its power needs, part of a plan by the technology company to become offset its carbon output.

The 175-megawatt wind farm is under construction 60 miles outside Chicago at the border of Kankakee and Iroquois Counties. It's 96 percent owned by EDF Renewable Energy, a U.S. subsidiary of French utility Electricite de France SA.

The wind farm will flow power onto the same same electric grid that powers Microsoft’s Chicago area datacenter and is expected to begin operating in 2015. The project is expected to supply enough electricity to power 70,000 homes in Illinois.

The 20-year agreement is Microsoft’s largest wind investment to date and follows on other similar investments by corporations looking to offset their energy needs with power sources that don’t release greenhouse gas. In November, the company announced it would buy power from a 110 megawatt wind farm in Texas. South of Chicago, in Vermilion County, IKEA is building a wind farm large enough to ensure that its stores will never have to buy power again.

Also, Facebook announced it would power its new Iowa data center using energy from a wind farm MidAmerican Energy is constructing. During the past few years, Google has been ticking up its wind power purchases and investing in wind projects in Iowa, Oklahoma and Texas.

“It is encouraging to see leading corporations investing in the US wind sector based not only on their desire to positively impact the environment, but also because it simply makes good business sense,” said Ryan Pfaff, executive vice president for EDF Renewable Energy.